Von Willebrand Disease
Von Willebrand Disease is a bleeding disorder caused by a defect or deficiency of a blood clotting protein, called von Willebrand Factor. The disease is estimated to occur in 1% to 2% of the population. The disease was first described by Erik von Willebrand, a Finnish physician who reported a new type of bleeding disorder among island people in Sweden and Finland.
Von Willebrand Factor is a protein critical to the initial stages of blood clotting. This glue-like protein, produced by the cells that line the blood vessel walls, interacts with blood cells called platelets to form a plug which prevents the blood from flowing at the site of injury. People with von Willebrand Disease are unable to make this plug because they do not have enough von Willebrand Factor or their factor is abnormal.
Researchers have identified many variations of the disease, but most fall into the following classifications:
• Type I: This is the most common and mildest form of von Willebrand disease. Levels of von Willebrand factor are lower than normal, and levels of factor VIII may also be reduced.
• Type II: In these people, the von Willebrand factor itself has an abnormality. Depending on the abnormality, they may be classified as having Type IIa or Type IIb. In Type IIa, the level of von Willebrand factor is reduced, as is the ability of platelets to clump together. In Type IIb, although the factor itself is defective, the ability of platelets to clump together is actually increased.
• Type III: This is severe von Willebrand disease. These people may have a total absence of von Willebrand factor, and factor VIII levels are often less than 10%.
• Pseudo (or platelet-type) von Willebrand disease: This disorder resembles Type IIb von Willebrand disease, but the defects appear to be in the platelets, rather than the von Willebrand factor.
Von Willebrand Disease is a genetic disease that can be inherited from either parent. It affects males and females equally. A man or woman with VWD has a 50% chance of passing the gene on to his or her child. There are no racial or ethnic associations with the disorder. A family history of a bleeding disorder is the primary risk factor.
VWD subtype I and II are usually inherited in what is known as a “dominant” pattern. This means that if even one parent has the gene and passes it to a child, the child will have the disorder.
VWD Type III von Willebrand disease, however, is usually inherited in a “recessive” pattern. This type occurs when the child inherits the gene from both parents. Even if both parents have mild or asymptomatic disease, their children are likely to be severely affected.
Diagnosis of von Willebrand Disease can be difficult. Blood tests can be performed to determine the amount, structure and function of von Willebrand Factor. Since levels can vary, sometimes tests may need to be repeated. A person suspected of having von Willebrand Disease should be referred to a hematologist who specializes in the diagnosis and treatment of bleeding disorders.
Usually, people with VWD bruise easily, have recurrent nosebleeds, or bleed after tooth extraction, tonsillectomy or other surgery. Recurrent nosebleeds are also a hallmark of VWD. Women can have increased menstrual bleeding.
For minor bleeds, treatment may be unnecessary. There are a range of treatment choices that depend on whether the VWD is mild or severe.
Stimate® or desmopressin acetate (DDAVP), a nasal spray, is the treatment of choice for mild von Willebrand disease. Bleeding is usually controlled in individuals with mild von Willebrand disease by using this nasal spray to boost their own factor VIII and von Willebrand levels. DDAVP may be given to increase the amount of the von Willebrand factor long enough for surgery or dental procedures to be performed. DDAVP is a synthetic product that carries no risk of infectious disease.
For excessive bleeding, infusions of a factor VIII concentrate rich in von Willebrand factor, such as Humate-P®, Alphanate® or Koate DVI®, may be required. Humate-P, manufactured by CSL-Behring and Alphanate, manufactured by Grifols, are the only FDA-approved Factor VIII concentrate for use in von Willebrand Disease.
If trauma occurs or surgery is anticipated, desmopressin acetate can be given as a means of raising the von Willebrand factor level.
Aspirin and many of the drugs used for pain can aggravate bleeding because they interfere with platelet function. People who have von Willebrand disease can take acetaminophen for pain relief because it does not inhibit platelet function.
The National Hemophilia Foundation’s Medical and Scientific Advisory Council (MASAC) issued a treatment recommendation for von Willebrand disease in 1999.
To access this recommendation, click here. To receive a copy of this recommendation, call 1-800-42HANDI.
The above information is courtesy of the National Hemophilia Foundation.